OK - this is sage advice I received from a real property developer...
Buy in a location you like - because if you get more than one BTL - you are going to be visiting it, probably more than you think.
Anyone who does BTL with multiple properties, ends up setting up a property management company too... So don't think its a buy it and leave it to the agent situation..
Find someone who does this already, that you know & trust... There are a LOT of things that aren't published on the internet, in how to make this really work for you... The best estate agents, lawyers, accountants and mortgage brokers are referred and if you are vouched for will show you how to arrange this in a manner where you ultimately can recoup your deposit.
I once got involved with an existing building, in certain zone, with a LLP, which allowed me to get a tax rebate equivalent to my deposit and after 5 years, I got my full investment including the deposit back, as well as my share of the profits from the property involved. Tax laws change and this one was identified by mr HMRC as not being in the spirit of what investments they were hoping for, but these types of situations do still arise given the right incentives in infrastructure are created by (a) govts looking to build their way out of bad situations and (b) tories. if anyone says anything about parties other than tories, all I will say is, we get more loopholes under labour, so I kinda miss those guys...
Anyway... Get talking to your inner circle and find the right contacts... Otherwise, the costs, the wrong agent, the awful tenant, the poor lawyer, or a useless broker, is going to make this much less profitable for you, assuming you can make a profit, given you are doing it leveraged.
Good luck...